1. Field of the Invention
This invention relates to an injecting unit for an injection molding machine, which unit comprises a carrying block, an axially movable plasticizing cylinder, which has a longitudinal axis and is so mounted in said carrying block that said longitudinal axis constitutes an injecting axis of said injecting unit, a rotatable feed screw, and automatable means for locking said plasticizing cylinder to said carrier block and for locking said feed screw to a motor for rotating said feed screw, which is axially movable into coupling interengagement with a profiled coupling section of said motor and for ejecting plasticized plastic material out of said cylinder.
2. Description of the Prior Art
An injecting unit of that kind is disclosed in U.S. Pat. No. 4,846,652. In that known unit the means for locking he Plasticizing cylinder and the feed screw comprise two locking sliders, which are guided on the carrying block of the injecting unit and normally extend into recesses formed in the plasticizing cylinder to lock the same. Coupling bridges are connected to said sliders and serve to lock the feed screw. Locking and unlocking functions can be performed regardless of the operating condition of the injecting unit. In that design a reliable fixation of the plasticizing cylinder to the carrying block cannot be ensured unless the plasticizing cylinder is formed with recesses for receiving the slider. But such recesses reduce the wall thickness of the plasticizing cylinder in that region. Even the slightest deviation of the dimensions of the recesses from the specified dimensions may render the operation of the sliders more difficult so that an expensive machining of the surfaces of the recesses is required.
For a long time, e.g., from U.S. Pat. No. 4,278,354, it has been known to lock a plasticizing cylinder at a stop of the carrying block by means of a nut and to operatively connect the feed screw to a profiled coupling section of a motor for rotating said feed screw. But in that case the feed screw has not been locked in conjunction with the locking of the plasticizing cylinder and such locking means have not been automatable thus far. Problems arise also in connection with the release of the plasticizing cylinder when it has become stuck to the carrying block and can be detached therefrom only by an exertion of a strong force with a heavy tool, possibly by a blow delivered to the plasticizing cylinder by means of a tool.